It was a hashtag that broke hearts and illuminated classrooms.
When #iwishmyteacherknew stormed the internet last year, spurring a wave of teachers to experiment with asking their pupils what they wished they knew, the result was as emotive as it was eye-opening.
There was Brittney in the sixth grade, who wrote:
"I wish my teacher knew my dad died this year, I feel more alone/disconnected from my peers than ever before."
And another, anonymous admission, carefully, falteringly written in pencil:
"I wish my teacher knew that we are low on money and have to go to a food bank to get food."
Or the quietly profound, written in stilted, non-cursive hand: "I wish my teacher knew that my dad works two jobs and I don't see him much."
Now, the hashtag's creator, third grade teacher Kyle Schwartz, has launched a book about the value of the question and how it has the power to bring teachers and families together to help foster learning and understanding.
In I Wish My Teacher Knew, the Doull Elementary School, Denver, Colorado teacher writes that the simple exercise she used as a way to get to know pupils almost never escaped the classroom, until a tweet catapulted Schwartz's lessons into the spotlight.
"As a first-year teacher, I worried about how much I didn't know about my students. I explained to them that I wanted to get to know them better. I wrote, 'I wish my teacher knew ...' on the board and asked them to complete the sentence," she explains.
"It was always a meaningful lesson for me, but the problem was that the power of the lesson stayed inside Room 207. I did not share the idea with my colleagues. I thought that a simple question wasn't important enough to share.
"That was until one night when my cat knocked over a basket and out tumbled a crumpled orange note I had saved. In shaky handwriting it read: 'I wish my teacher knew I don't have pencils at home to do my homework.'
"As I reread those words, I felt the same ache as the first time I had read them. I thought of my former student, and how even though she didn't always have access to basic resources, she still came to school every day so willing to try, willing to struggle, and willing to learn."
After tweeting the picture, a phenomenon was born, with teachers and students across the States and beyond asking and answering the question.
Attention was finally being given to problems and insights that for too long had remained at home, discrete from school life.
"It should make headline news that there are so many dedicated students who do not have pencils at home, but it doesn't," she writes in the book.
"There should be outrage that many American children attend schools that lack necessary resources to teach them.
"We need to demand change. We must take action, both inside and outside the classroom, so that the American public education system is worthy of the brilliant students it serves.
"Harnessing the collective power of the voices of teachers, students, and their families is our best chance of creating the equitable system our country needs.
"Imagine a world in which every child's potential is valued; where every child receives the excellent education they deserve.
"What would our government look like? What would our neighbourhoods look like? What would our schools look like? What would our classrooms look like? What would school be like if we asked students to tell us what we adults don't know?"